Afebrile Influenza in Healthcare Workers

By Amesh A. Adalja MD FACP FACEP May 29, 2015

One of the chief means of arresting the spread of influenza through healthcare facilities is vaccination of healthcare workers—a practice that is increasingly become routinized and even mandated. In addition to vaccination of healthcare workers, it is recommended that those with fever and respiratory symptoms be excused from work until they are afebrile for 24 hours (without the use of antipyretics) as it is thought the febrile are more apt to transmit infection.

A new study from the University of Chicago, published in Clinical Infectious Diseases, challenges that paradigm.

Half afebrile

Prompted by a nosocomial influenza case traced to an afebrile healthcare worker with respiratory symptoms who tested positive for influenza, Ridgway et al. conducted a study during a 2-month period in 2014 in which all healthcare workers with respiratory symptoms were tested for respiratory pathogens by multiplex PCR. Temperature was also measured to assess for fever.

In total 458 workers were tested. Positive results were obtained in 54% with 18% having a history of fever or a documented fever. Coronavirus, influenza, and RSV were the most commonly identified microorganisms.

Of the 41 workers infected with influenza, just 51.2% were febrile. Seasonal vaccination had been obtained by 20 of them while 18 declined (3 had unknown vaccination status). All those with influenza reported cough. Interestingly, a trend towards afebrile illness was reported among those who had been vaccinated.

Policy Modification Needed?

This study has a very important implication that will likely impact hospital infection control policy. If fever is the sole triggering sign or symptom used to exclude a healthcare worker with respiratory illness from duties, a substantial risk remains for nosocomial influenza transmission to patients and other healthcare workers persists. As Ridgway and colleagues note, hospitals may need to more extensively test afebrile workers with respiratory symptoms or have broader workplace exclusion policies in order to optimize patient safety, both of which will come at considerable costs to hospitals.